Catch the GG Transit into San Rafael; then take a city bus to Muir Woods or Mill Valley. You can see Mt Tam towering over MV and MW. Very, very cool. Theres an AMAZING walk in hostel on the slopes with virtually no employees: food, drink, etc laying around in plain sight. Several plane wrecks there: it has kind of a shifty vibe because serial killers have operated there for several decades. No, no precise gps coordinates but if you look online, sites will tell you which trails are interesting.